Commit Graph

1834 Commits

Author SHA1 Message Date
Philip Reames a40162d475 [Tests] Add a SCEV analysis test for llvm.widenable.condition
Mostly because we don't appear to have one and a prototype patch I just saw would have broken the example committed.

llvm-svn: 374835
2019-10-14 22:42:35 +00:00
Simon Pilgrim 1385b27e92 [CostModel][X86] Add CTLZ scalar costs
Add specific scalar costs for CTLZ instructions, we can't discriminate between CTLZ and CTLZ_ZERO_UNDEF so we have to assume the worst. Given how BSR is often a microcoded nightmare on some older targets we might still be underestimating it.

For targets supporting LZCNT (Intel Haswell+ or AMD Fam10+), we provide overrides that assume 1cy costs.

llvm-svn: 374786
2019-10-14 16:30:17 +00:00
Simon Pilgrim 151bbba758 [CostModel][X86] Add CTPOP scalar costs (PR43656)
Add specific scalar costs for ctpop instructions, these are based on the llvm-mca's SLM throughput numbers (the oldest model we have).

For targets supporting POPCNT, we provide overrides that assume 1cy costs.

llvm-svn: 374775
2019-10-14 14:07:43 +00:00
Simon Pilgrim 1b59a16c0b [CostModel][X86] Improve sum reduction costs.
I can't see any notable differences in costs between SSE2 and SSE42 arches for FADD/ADD reduction, so I've lowered the target to just SSE2.

I've also added vXi8 sum reduction costs in line with the PSADBW codegen and discussions on PR42674.

llvm-svn: 374655
2019-10-12 13:21:50 +00:00
Alina Sbirlea 6442b56974 [MemorySSA] Update Phi simplification.
When simplifying a Phi to the unique value found incoming, check that
there wasn't a Phi already created to break a cycle. If so, remove it.
Resolves PR43541.

Some additional nits included.

llvm-svn: 374471
2019-10-10 23:27:21 +00:00
Alina Sbirlea 67f0c5c085 [MemorySSA] Additional handling of unreachable blocks.
Summary:
Whenever we get the previous definition, the assumption is that the
recursion starts ina  reachable block.
If the recursion starts in an unreachable block, we may recurse
indefinitely. Handle this case by returning LoE if the block is
unreachable.

Resolves PR43426.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68809

llvm-svn: 374447
2019-10-10 20:43:06 +00:00
Alina Sbirlea 7faa14a98b [MemorySSA] Make the use of moveAllAfterMergeBlocks consistent.
Summary:
The rule for the moveAllAfterMergeBlocks API si for all instructions
from `From` to have been moved to `To`, while keeping the CFG edges (and
block terminators) unchanged.
Update all the callsites for moveAllAfterMergeBlocks to follow this.

Pending follow-up: since the same behavior is needed everytime, merge
all callsites into one. The common denominator may be the call to
`MergeBlockIntoPredecessor`.

Resolves PR43569.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68659

llvm-svn: 374177
2019-10-09 15:54:24 +00:00
Simon Pilgrim d7ac255325 [CostModel][X86] Add tests for insertelement to non-immediate vector element indices
llvm-svn: 374161
2019-10-09 12:36:34 +00:00
Simon Pilgrim a21176ffb1 [CostModel][X86] Add tests for extractelement from non-immediate vector element indices
llvm-svn: 374160
2019-10-09 12:36:22 +00:00
Alina Sbirlea 145cdad119 [MemorySSA] Don't hoist stores if interfering uses (as calls) exist.
llvm-svn: 373674
2019-10-03 22:20:04 +00:00
Alina Sbirlea 24ae5ce54b [MemorySSA] Update Phi creation when inserting a Def.
MemoryPhis should be added in the IDF of the blocks newly gaining Defs.
This includes the blocks that gained a Phi and the block gaining a Def,
if the block did not have one before.
Resolves PR43427.

llvm-svn: 373505
2019-10-02 18:42:33 +00:00
Bardia Mahjour 91b62d5c89 [DDG] Data Dependence Graph - Root Node
Summary:
This patch adds Root Node to the DDG. The purpose of the root node is to create a single entry node that allows graph walk iterators to iterate through all nodes of the graph, making sure that no node is left unvisited during a graph walk (eg. SCC or DFS). Once the DDG is fully constructed it will have exactly one root node. Every node in the graph is reachable from the root. The algorithm for connecting the root node is based on depth-first-search that keeps track of visited nodes to try to avoid creating unnecessary edges.

Authored By: bmahjour

Reviewer: Meinersbur, fhahn, myhsu, xtian, dmgreen, kbarton, jdoerfert

Reviewed By: Meinersbur

Subscribers: ychen, arphaman, simoll, a.elovikov, mgorny, hiraditya, jfb, wuzish, llvm-commits, jsji, Whitney, etiotto, ppc-slack

Tag: #llvm

Differential Revision: https://reviews.llvm.org/D67970

llvm-svn: 373386
2019-10-01 19:32:42 +00:00
Alina Sbirlea 890090f7f5 [MemorySSA] Check for unreachable blocks when getting last definition.
If a single predecessor is found, still check if the block is
unreachable. The test that found this had a self loop unreachable block.
Resolves PR43493.

llvm-svn: 373383
2019-10-01 19:09:50 +00:00
Alina Sbirlea ae40dfc1e3 [MemorySSA] Update last_access_in_block check.
The check for "was there an access in this block" should be: is the last
access in this block and is it not a newly inserted phi.
Resolves new test in PR43438.

Also fix a typo when simplifying trivial Phis to match the comment.

llvm-svn: 373380
2019-10-01 18:34:39 +00:00
Evandro Menezes 22cb3d2e58 [ConstantFolding] Fold constant calls to log2()
Somehow, folding calls to `log2()` with a constant was missing.

Differential revision: https://reviews.llvm.org/D67300

llvm-svn: 373262
2019-09-30 20:53:23 +00:00
Tim Northover 58e8c793d0 Revert "[SCEV] add no wrap flag for SCEVAddExpr."
This reverts r366419 because the analysis performed is within the context of
the loop and it's only valid to add wrapping flags to "global" expressions if
they're always correct.

llvm-svn: 373184
2019-09-30 07:46:52 +00:00
Simon Pilgrim d7f0207d73 [CostModel][X86] Fix SLM <2 x i64> icmp costs
SLM is 2 x slower for <2 x i64> comparison ops than other vector types, we should account for this like we do for SLM <2 x i64> add/sub/mul costs.

This should remove some of the SLM codegen diffs in D43582

llvm-svn: 372954
2019-09-26 10:14:38 +00:00
Alina Sbirlea 6720ed851b [MemorySSA] Avoid adding Phis in the presence of unreachable blocks.
Summary:
If a block has all incoming values with the same MemoryAccess (ignoring
incoming values from unreachable blocks), then use that incoming
MemoryAccess and do not create a Phi in the first place.

Revert IDF work-around added in rL372673; it should not be required unless
the Def inserted is the first in its block.

The patch also cleans up a series of tests, added during the many
iterations on insertDef.

The patch also fixes PR43438.
The same issue that occurs in insertDef with "adding phis, hence the IDF of
Phis is needed", can also occur in fixupDefs: the `getPreviousRecursive`
call only adds Phis walking on the predecessor edges, which means there
may be the case of a Phi added walking the CFG "backwards" which
triggers the needs for an additional Phi in successor blocks.
Such Phis are added during fixupDefs only in the presence of unreachable
blocks.
Hence this highlights the need to avoid adding Phis in blocks with
unreachable predecessors in the first place.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67995

llvm-svn: 372932
2019-09-25 23:24:39 +00:00
Alina Sbirlea 2c5e6646ef [MemorySSA] Update Phi insertion.
Summary:
MemoryPhis may be needed following a Def insertion inthe IDF of all the
new accesses added (phis + potentially a def). Ensure this also  occurs when
only the new MemoryPhis are the defining accesses.

Note: The need for computing IDF here is because of new Phis added with
edges incoming from unreachable code, Phis that had previously been
simplified. The preferred solution is to not reintroduce such Phis.
This patch is the needed fix while working on the preferred solution.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67927

llvm-svn: 372673
2019-09-23 23:50:16 +00:00
Simon Pilgrim 4d486156e7 [Cost][X86] Add more missing vector truncation costs
The AVX512 cases still need some work to correct recognise the PMOV truncation cases.

llvm-svn: 372514
2019-09-22 16:46:15 +00:00
Simon Pilgrim 665ccbff60 [Cost][X86] Add v2i64 truncation costs
We are missing costs for a lot of truncation cases, I'm hoping to address all the 'zero cost' cases in trunc.ll

I thought this was a vector widening side effect, but even before this we had some interesting LV decisions (notably over indvars) being made due to these zero costs.

llvm-svn: 372498
2019-09-22 12:04:38 +00:00
Ulrich Weigand 819c1651f7 [SystemZ] Support z15 processor name
The recently announced IBM z15 processor implements the architecture
already supported as "arch13" in LLVM.  This patch adds support for
"z15" as an alternate architecture name for arch13.

The patch also uses z15 in a number of places where we used arch13
as long as the official name was not yet announced.

llvm-svn: 372435
2019-09-20 23:04:45 +00:00
Shoaib Meenai d89f2d872d [Analysis] Allow -scalar-evolution-max-iterations more than once
At present, `-scalar-evolution-max-iterations` is a `cl::Optional`
option, which means it demands to be passed exactly zero or one times.
Our build system makes it pretty tricky to guarantee this. We often
accidentally pass the flag more than once (but always with the same
value) which results in an error, after which compilation fails:

```
clang (LLVM option parsing): for the -scalar-evolution-max-iterations option: may only occur zero or one times!
```

It seems reasonable to allow -scalar-evolution-max-iterations to be
passed more than once. Quoting the [[ http://llvm.org/docs/CommandLine.html#controlling-the-number-of-occurrences-required-and-allowed | documentation ]]:

> The cl::ZeroOrMore modifier ... indicates that your program will allow the option to be specified zero or more times.
> ...
> If an option is specified multiple times for an option of the cl::opt class, only the last value will be retained.

Original patch by: Enrico Bern Hardy Tanuwidjaja <etanuwid@fb.com>

Differential Revision: https://reviews.llvm.org/D67512

llvm-svn: 372346
2019-09-19 18:21:32 +00:00
Bardia Mahjour db800c267d Data Dependence Graph Basics
Summary:
This is the first patch in a series of patches that will implement data dependence graph in LLVM. Many of the ideas used in this implementation are based on the following paper:
D. J. Kuck, R. H. Kuhn, D. A. Padua, B. Leasure, and M. Wolfe (1981). DEPENDENCE GRAPHS AND COMPILER OPTIMIZATIONS.
This patch contains support for a basic DDGs containing only atomic nodes (one node for each instruction). The edges are two fold: def-use edges and memory-dependence edges.
The implementation takes a list of basic-blocks and only considers dependencies among instructions in those basic blocks. Any dependencies coming into or going out of instructions that do not belong to those basic blocks are ignored.

The algorithm for building the graph involves the following steps in order:

  1. For each instruction in the range of basic blocks to consider, create an atomic node in the resulting graph.
  2. For each node in the graph establish def-use edges to/from other nodes in the graph.
  3. For each pair of nodes containing memory instruction(s) create memory edges between them. This part of the algorithm goes through the instructions in lexicographical order and creates edges in reverse order if the sink of the dependence occurs before the source of it.

Authored By: bmahjour

Reviewer: Meinersbur, fhahn, myhsu, xtian, dmgreen, kbarton, jdoerfert

Reviewed By: Meinersbur, fhahn, myhsu

Subscribers: ychen, arphaman, simoll, a.elovikov, mgorny, hiraditya, jfb, wuzish, llvm-commits, jsji, Whitney, etiotto

Tag: #llvm

Differential Revision: https://reviews.llvm.org/D65350

llvm-svn: 372238
2019-09-18 17:43:45 +00:00
Jay Foad c92e51d84b [SDA] Don't stop divergence propagation at the IPD.
Summary:
This fixes B42473 and B42706.

This patch makes the SDA propagate branch divergence until the end of the RPO traversal. Before, the SyncDependenceAnalysis propagated divergence only until the IPD in rpo order. RPO is incompatible with post dominance in the presence of loops. This made the SDA crash because blocks were missed in the propagation.

Reviewers: foad, nhaehnle

Reviewed By: foad

Subscribers: jvesely, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65274

llvm-svn: 372223
2019-09-18 13:40:22 +00:00
Bardia Mahjour 6476d7cf0b Revert "Data Dependence Graph Basics"
This reverts commit c98ec60993, which broke the sphinx-docs build.

llvm-svn: 372168
2019-09-17 19:22:01 +00:00
Bardia Mahjour c98ec60993 Data Dependence Graph Basics
Summary:
This is the first patch in a series of patches that will implement data dependence graph in LLVM. Many of the ideas used in this implementation are based on the following paper:
D. J. Kuck, R. H. Kuhn, D. A. Padua, B. Leasure, and M. Wolfe (1981). DEPENDENCE GRAPHS AND COMPILER OPTIMIZATIONS.
This patch contains support for a basic DDGs containing only atomic nodes (one node for each instruction). The edges are two fold: def-use edges and memory-dependence edges.
The implementation takes a list of basic-blocks and only considers dependencies among instructions in those basic blocks. Any dependencies coming into or going out of instructions that do not belong to those basic blocks are ignored.

The algorithm for building the graph involves the following steps in order:

  1. For each instruction in the range of basic blocks to consider, create an atomic node in the resulting graph.
  2. For each node in the graph establish def-use edges to/from other nodes in the graph.
  3. For each pair of nodes containing memory instruction(s) create memory edges between them. This part of the algorithm goes through the instructions in lexicographical order and creates edges in reverse order if the sink of the dependence occurs before the source of it.

Authored By: bmahjour

Reviewer: Meinersbur, fhahn, myhsu, xtian, dmgreen, kbarton, jdoerfert

Reviewed By: Meinersbur, fhahn, myhsu

Subscribers: ychen, arphaman, simoll, a.elovikov, mgorny, hiraditya, jfb, wuzish, llvm-commits, jsji, Whitney, etiotto

Tag: #llvm

Differential Revision: https://reviews.llvm.org/D65350

llvm-svn: 372162
2019-09-17 18:55:44 +00:00
Alina Sbirlea 4e9082ef95 [MemorySSA] Fix phi insertion when inserting a def.
Summary:
When inserting a Def, the current algorithm is walking edges backward
and inserting new Phis where needed. There may be additional Phis needed
in the IDF of the newly inserted Def and Phis.
Adding Phis in the IDF of the Def was added ina  previous patch, but we
may also need other Phis in the IDF of the newly added Phis.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67637

llvm-svn: 372138
2019-09-17 16:33:35 +00:00
Alina Sbirlea 6b2d1346d8 [MemorySSA] Update MSSA for non-conventional AA.
Summary:
Regularly when moving an instruction that may not read or write memory,
the instruction is not modelled in MSSA, so not action is necessary.
For a non-conventional AA pipeline, MSSA needs to explicitly check when
creating accesses, so as to not model instructions that may not read and
write memory.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67562

llvm-svn: 372137
2019-09-17 16:31:37 +00:00
David Bolvansky e80fcf0340 [SimplifyLibCalls] Mark known arguments with nonnull
Reviewers: efriedma, jdoerfert

Reviewed By: jdoerfert

Subscribers: ychen, rsmith, joerg, aaron.ballman, lebedev.ri, uenoku, jdoerfert, hfinkel, javed.absar, spatel, dmgreen, llvm-commits

Differential Revision: https://reviews.llvm.org/D53342

llvm-svn: 372091
2019-09-17 09:32:52 +00:00
Bardia Mahjour 474c713fc7 [NFC] Test commit access
llvm-svn: 372033
2019-09-16 20:44:15 +00:00
Philip Reames bdf608477e [SCEV] Add smin support to getRangeRef
We were failing to compute trip counts (both exact and maximum) for any loop which involved a comparison against either an umin or smin. It looks like this simply got missed when we added smin/umin to SCEV.  (Note: umin was submitted separately earlier today.  Turned out two folks hit this at the same time.)

Differential Revision: https://reviews.llvm.org/D67514

llvm-svn: 371776
2019-09-12 21:32:27 +00:00
Evandro Menezes 08df6e64d5 [ConstantFolding] Expand folding of some library functions
Expanding the folding of `nearbyint()`, `rint()` and `trunc()` to library
functions, in addition to the current support for intrinsics.

Differential revision: https://reviews.llvm.org/D67468

llvm-svn: 371774
2019-09-12 21:23:22 +00:00
Florian Hahn a31ee37624 [SCEV] Support SCEVUMinExpr in getRangeRef.
This patch adds support for SCEVUMinExpr to getRangeRef,
similar to the support for SCEVUMaxExpr.

Reviewers: sanjoy.google, efriedma, reames, nikic

Reviewed By: sanjoy.google

Differential Revision: https://reviews.llvm.org/D67177

llvm-svn: 371768
2019-09-12 20:03:32 +00:00
Philip Reames a3d2737520 Precommit tests for D67514
llvm-svn: 371762
2019-09-12 19:34:27 +00:00
Alina Sbirlea 6943472d45 [MemorySSA] Pass (for update) MSSAU when hoisting instructions.
Summary: Pass MSSAU to makeLoopInvariant in order to properly update MSSA.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, uabelho, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67470

llvm-svn: 371748
2019-09-12 17:12:51 +00:00
Alina Sbirlea f7b4022db1 [MemorySSA] Do not create memoryaccesses for debug info intrinsics.
Summary:
Do not model debuginfo intrinsics in MemorySSA.
Regularly these are non-memory modifying instructions. With -disable-basicaa, they were being modelled as Defs.

Reviewers: george.burgess.iv

Subscribers: aprantl, Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67307

llvm-svn: 371565
2019-09-10 22:35:27 +00:00
Guozhi Wei b329e0728b [BPI] Adjust the probability for floating point unordered comparison
Since NaN is very rare in normal programs, so the probability for floating point unordered comparison should be extremely small. Current probability is 3/8, it is too large, this patch changes it to a tiny number.

Differential Revision: https://reviews.llvm.org/D65303

llvm-svn: 371541
2019-09-10 17:25:11 +00:00
Evandro Menezes 88a98ea3f7 [ConstantFolding] Add new test cases for transcendentals (NFC)
llvm-svn: 371246
2019-09-06 19:41:49 +00:00
Alina Sbirlea ae900d3882 [MemorySSA] Update MemorySSA when removing debug.value calls.
llvm-svn: 371084
2019-09-05 16:25:24 +00:00
Simon Pilgrim cacf4db571 [CostModel][X86] Add scalar sext/zext cost tests
llvm-svn: 370684
2019-09-02 21:02:51 +00:00
Alina Sbirlea 3d03769ba0 [MemorySSA] Rename all phi entries.
When renaming Phis incoming values, there may be multiple edges incoming
from the same block (switch). Rename all.

llvm-svn: 370548
2019-08-30 23:02:53 +00:00
Roman Lebedev cc95a45f8a [CostModel] Model all `extractvalue`s as free.
Summary:
As disscussed in https://reviews.llvm.org/D65148#1606412,
`extractvalue` don't actually generate any code,
so we should treat them as free.

Reviewers: craig.topper, RKSimon, jnspaulsson, greened, asb, t.p.northover, jmolloy, dmgreen

Reviewed By: jmolloy

Subscribers: javed.absar, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66098

llvm-svn: 370339
2019-08-29 11:50:30 +00:00
Alina Sbirlea 228ffac678 [MemorySSA] Fix insertUse.
Actually call the renamePass on inserted Phis.
Fixes PR42940.

Subscribers: llvm-commits
llvm-svn: 369997
2019-08-27 00:34:47 +00:00
Roland Froese 18db4e9ae1 Recommit [PowerPC] Update P9 vector costs for insert/extract
Now that the v1i128 smin regression has been fixed, recommit the P9 cost
updates from D60160.

llvm-svn: 369952
2019-08-26 19:26:08 +00:00
Johannes Doerfert 22e6e108e1 [BasicAA] Use dereferenceability to reason about aliasing
Summary:
We already use the fact that an object with known size X does not alias
another objection of size Y > X before. With this commit, we use
dereferenceability information to determine a lower bound for Y and not
only rely on the user provided query size.

The result for @global_and_deref_arg_2() and @local_and_deref_ret_2()
in test/Analysis/BasicAA/dereferenceable.ll improved with this patch.

Reviewers: asbirlea, chandlerc, hfinkel, sanjoy

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66157

llvm-svn: 369786
2019-08-23 17:56:10 +00:00
Johannes Doerfert a5b10b464e [MustExec] Add a generic "must-be-executed-context" explorer
Given an instruction I, the MustBeExecutedContextExplorer allows to
easily traverse instructions that are guaranteed to be executed whenever
I is. For now, these instruction have to be statically "after" I, in
the same or different basic blocks.

This patch also adds a pass which prints the must-be-executed-context
for each instruction in a module. It is used to test the
MustBeExecutedContextExplorer, for now on the examples given in the
class comment of the MustBeExecutedIterator.

Differential Revision: https://reviews.llvm.org/D65186

llvm-svn: 369765
2019-08-23 15:17:27 +00:00
Craig Topper d420616313 [X86] Lower the cost of v2i32->v2f64 sint_to_fp under vector widening legalization.
I don't really understand the costs we're using for fp_to_sint,
but prior to widening legalization we used 20 as the cost for this
via the v2i64->v2f64 entry. That number seems better than the 40
we got with widening legalization. So now we need either a
v2i32->v2f64 entry or a v4i32->v2f64 entry depending on whether
AVX is enabled or not since we skip the first SSE2 table look up
under AVX.

llvm-svn: 369628
2019-08-22 08:18:45 +00:00
Alina Sbirlea 7425179fee [LoopPassManager + MemorySSA] Only enable use of MemorySSA for LPMs known to preserve it.
Summary:
Add a flag to the FunctionToLoopAdaptor that allows enabling MemorySSA only for the loop pass managers that are known to preserve it.

If an LPM is known to have only loop transforms that *all* preserve MemorySSA, then use MemorySSA if `EnableMSSALoopDependency` is set.
If an LPM has loop passes that do not preserve MemorySSA, then the flag passed is `false`, regardless of the value of `EnableMSSALoopDependency`.

When using a custom loop pass pipeline via `passes=...`, use keyword `loop` vs `loop-mssa` to use MemorySSA in that LPM. If a loop that does not preserve MemorySSA is added while using the `loop-mssa` keyword, that's an error.

Add the new `loop-mssa` keyword to a few tests where a difference occurs when enabling MemorySSA.

Reviewers: chandlerc

Subscribers: mehdi_amini, Prazek, george.burgess.iv, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66376

llvm-svn: 369548
2019-08-21 17:00:57 +00:00
Alina Sbirlea 1c528e8f1b [MemorySSA] Fix existing phis when inserting defs.
Summary:
When inserting a new Def, and inserting Phis in the IDF when needed,
also mark the already existing Phis in the IDF as non-optimized, since
these may need fixing as well.
In the test attached, there is a Phi in the IDF that happens to be
trivial, and is wrongfully removed by the call to getLastDef that
follows. This is a valid situation and the existing IDF Phis need to
marked as "may need fixing" as well.
Resolves PR43044.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66495

llvm-svn: 369464
2019-08-20 22:29:06 +00:00